Make postgresql faster on development (thanks to @tapajos).

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -122,6 +122,14 @@ def simplified_type(field_type)
         # Extracts the value from a PostgreSQL column default definition.
         def self.extract_value_from_default(default)
           case default
+            # This is a performance optimization for Ruby 1.9.2 in development.
+            # If the value is nil, we return nil straight away without checking
+            # the regular expressions. If we check each regular expression,
+            # Regexp#=== will call NilClass#to_str, which will trigger
+            # method_missing (defined by whiny nil in ActiveSupport) which
+            # makes this method very very slow.
+            when NilClass
+              nil
             # Numeric types
             when /\A\(?(-?\d+(\.\d*)?\)?)\z/
               $1